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Originally published as:

Henri Bergson. "The Intensity of Psychic States".
Chapter 1 in Time and Free Will: An Essay on the Immediate Data of
Consciousness, translated by F.L. Pogson, M.A. London: George Allen
and Unwin (1910): 1-74.

Editors' notes

We have included Time and Free Will as background to
Mead's lecture on it in Movements of Thought in the Nineteenth
Century. We apologize for the awkward layout but we thougt the side
notes were important to preserve.

Time and Free Will:
An Essay on the Immediate Data of Consciousness

Chapter 1: The Intensity of Psychic States

Henri Bergson

IT is
usually admitted that states of consciousness, sensations, feelings,
passions, efforts, are capable of growth and diminution; we are even
told that a sensation can be said to be twice, thrice, four times as intense? as another
sensation of the same kind. This latter thesis, which is maintained by
psychophysicists, we shall examine later ; but even the opponents of
psychophysics do not see any harm in speaking of one sensation as being
more intense than another, of one effort as being greater than another,
and in thus setting up differences of quantity between purely internal
states. Common sense, moreover, has not the slightest hesitation in
giving its verdict on this point ; people say they are more or less
warm, or more or less sad, and this distinction of more and less, even
when it is carried over to the region of subjective facts and unextended
objects, surprises nobody. But this involves a very obscure point and a
much more important problem than is usually supposed.

When we assert that one number is greater than

Such differences applicable
to magnitudes but not to intensities

(2) another number or
one body greater than anotherbody, we know very well what we
mean. For in both cases we allude to unequal spaces, as shall be shown
in detail a little further on, and we call that space the greater which
contains the other. But how can a more intense sensation contain one of
less intensity ? Shall we say that the first implies the second, that we
reach the sensation of higher intensity only on condition of having
first passed through the less intense stages of the same sensation, and
that in a certain sense we are concerned, here also, with the relation
of container to contained ? This conception of intensive magnitude
seems, indeed, to be that of common sense, but we cannot advance it as a
philosophical explanation without becoming involved in a vicious circle.
For it is beyond doubt that, in the natural series of numbers, the later
number exceeds the earlier, but the very possibility of arranging the
numbers in ascending order arises from their having to each other
relations of container and contained, so that we feel ourselves able to
explain precisely in what sense one is greater than the other. The
question, then, is how we succeed in forming a series of this kind with
intensities, which cannot be superposed on each other, and by what sign
we recognize that the members of this series increase, for example,
instead of diminishing : but this always comes back to the-inquiry, why
an intensity can be assimilated to a magnitude.

(3)

Alleged distinctions between two kinds of quantity:
extensive and intensive magnitude.

It is only to evade the difficulty to distinguish, as is usually
done, between two species of quantity, the first extensive and
measurable, the second intensive and not admitting of measure, but of
which it can nevertheless less be said that it is greater or less than.
another intensity. For it is recognized thereby that there is
something common to these two forms of magnitude, since they are both
termed magnitudes and declared to be equally capable of increase and
diminution. But, from the point of view of magnitude, what can there be
in common between the extensive and the intensive, the extended and the
unextended ? If, in the first case, we call that which contains the
other the greater quantity, why go on speaking of quantity and magnitude
when there is no longer a container or a contained? If a quantity can
increase and diminish, if we perceive in it, so to speak, the less inside
the more, is not such a quantity on this very account divisible,
and thereby extended ? Is it not then a contradiction to speak of an
inextensive quantity ? But yet common sense agrees with the philosophers
in setting up a pure intensity as a magnitude, just as if it were
something extended. And not only do we use the same word, but whether we
think of a greater intensity or a greater extensity, we experience in
both cases an analogous impression ; the terms " greater " and
" less " call up in both cases the same idea.

(4) If we now ask ourselves in what does this idea
consist, our consciousness still offers us the image of a container and
a contained. We picture to ourselves, for example, a greater intensity
of effort as a greater length of thread rolled up, or as a spring which,
in unwinding, will occupy a greater space. In the idea of intensity, and
even in the word which expresses it, we shall find the image of a
present contraction and consequently a future expansion, the image of
something virtually extended, and, if we may say so, of a compressed
space. We are thus led to believe that we translate the intensive into
the extensive, and that we compare two intensities, or at least express
the comparison, by the confused intuition of a relation between two
extensities. But it is just the nature of this operation which it is
difficult to determine.

Attempt to distinguish
intensities by objective causes. But we judge of intensity without
knowning magnitud or nature of the cause.

The solution which occurs immediately to the mind, once it
has entered upon this path, consists in defining the intensity of a
sensation, or of any state whatever of the ego, bythe number and
magnitude of the objective, and therefore measurable, causes which have
given rise to it. Doubtless, a more intense sensation of light is the
one which has been obtained, or is obtainable, by means of a
larger number of luminous sources, provided they be at the same distance
and identical with one another. But, in the immense majority of cases,
we decide about

(5) the intensity of the effect without even knowing the
nature of the cause, much less its magnitude indeed, it is the very
intensity of the effect which often leads us to venture an hypothesis as
to the number and nature of the causes, and thus to revise the judgment
of our senses, which at first represented them as insignificant. And it
is no use arguing that we are then comparing the actual state of the ego
with some previous state in which the cause was perceived in its
entirety at the same time as its effect was experienced. No doubt this
is our procedure in a fairly large number of cases ; but we cannot then
explain the differences of intensity which we recognize between
deep-seated psychic phenomena, the cause of which is within us and not
outside. On the other hand, we are never so bold in judging the
intensity of a psychic state as when the subjective aspect of the
phenomenon is the only one to strike us, or when the external cause to
which we refer it does not easily admit of measurement. Thus it seems
evident that we experience a more intense pain at the pulling out of a
tooth than of a hair ; the artist knows without the possibility of doubt
that the picture of a master affords him more intense pleasure than the
signboard of a shop ; and there is not the slightest need ever to have
heard of forces of cohesion to assert that we expend less effort in
bending a steel black than a bar of iron. Thus the comparison of two
intensities is usually made without the least appreciation of the

(6) number of causes, their mode of action or their
extent.

Attempt to distinguish
intensities by atomic movements But it is the sensation which is given
in consciousness, and not the movement.

There is still room, it is true, for an hypothesis of the same
nature, but more subtle. We know that mechanical, and especially
kinetic, theories aim at explaining the visible and sensible properties
of bodies by well defined movements of their ultimate parts, and many of
us foresee the time when the intensive differences of qualities,
that is to say, of our sensations, will be reduced to extensive
differences between the changes taking place behind them. May it not be
maintained that, without knowing these theories, we have a vague surmise
of them, that behind the more intense sound we guess the presence of
ampler vibrations which are propagated in the disturbed medium, and that
it is with a reference to this mathematical relation, precise in itself
though confusedly perceived, that we assert the higher intensity of a
particular sound ? Without even going so far, could it not be laid down
that every state of consciousness corresponds to a certain disturbance
of the molecules and atoms of the cerebral substance, and that the
intensity of a sensation measures the amplitude, the complication or the
extent of these molecular movements ? This last hypothesis is at least
as probable as the other, but it no more solves the problem. For, quite
possibly, the intensity of a sensation bears witness to a more or

(7) less considerable work accomplished in our organism ;
but it is the sensation which is given to us in consciousness, and not
this mechanical work. Indeed, it is by the intensity of the sensation
that we judge of the greater or less amount of work accomplished:
intensity then remains, at least apparently, a property of sensation.
And still the same question recurs : why do we say of a higher intensity
that it is greater ? Why do we think of a greater quantity or a greater
space ?

Different kinds of
intensities. (1) deep-seated psychic states (2) muscular effort.
Intensity is more easily definable in the former case.

Perhaps the difficulty of the problem lies chiefly in the
fact that we call by the same name, and picture to ourselves in the same
way, intensities which are very different in nature, e.g. the intensity
of a feeling and that of a sensation or an effort. The effort is
accompanied by a muscular sensation, and the sensations themselves case'
are connected with certain physical conditions which probably count for
something in the estimate of their intensity : we have here to do with
phenomena which take place on the surface of consciousness, and which
are always connected, as we shall see further on, with the perception of
a movement or of an external object. But certain states of the soul seem
to us, rightly or wrongly, to be self-sufficient, such as deep joy or
sorrow, a reflective passion or an aesthetic emotion Pure intensity
ought to be more easily

(8) definable in these simple cases, where no extensive
clement seems to be involved. We shall see, in fact, that it is
reducible here to a certain quality or shade which spreads over a more
or less considerable mass of psychic states, or, if the expression be
preferred, to the larger or smaller number of simple states which make
up the fundamental emotion.

Take, for example, the
progress of a desire

For example, an obscure desire gradually becomes a deep
passion. Now, you will see that the feeble intensity of this desire
consisted at first in its appearing to be isolated and, as it were,
foreign to the remainder of your inner life. But little by little it
permeates a larger number of psychic elements, tingeing them, so to
speak, with its own colour and lo! your outlook on the whole of your
surroundings seems now to have changed radically. How do you become
aware of a deep passion, once it has taken hold of you, if not by
perceiving that the same objects no longer impress you in the same
manner ? All your sensations and all your ideas seem to brighten up: it
is like childhood back again. We experience something of the kind in
certain dreams, in which we do not imagine anything out of the ordinary,
and yet through which there resounds an indescribable note of
originality. The fact is that, the further we penetrate into the depths
of consciousness, the less right we have to treat psychic phenomena as
things which are set side

(9) by side. When it is said that an object occupies
a large space in the soul or even that it fills it entirely, we ought to
understand by this simply that its image has altered the shade of a
thousand perceptions or memories, and that in this sense it pervades
them, although it does not itself come into view. But this wholly
dynamic way of looking at things is repugnant to the reflective
consciousness, because the latter delights in clean cut distinctions,
which are easily expressed in words, and in things with well-defined
outlines, like those which are perceived in space. It will assume then
that, everything else remaining identical, such and such a desire has
gone up a scale of magnitudes, as though it were permissible still to
speak of magnitude where there is neither multiplicity nor space 1 But
just as consciousness (as will be shown later on) concentrates on a
given point of the organism the increasing number of muscular
contractions which take place on the surface of the body, thus
converting them into one single feeling of effort, of growing intensity,
so it will hypostatize under the form of a growing desire the gradual
alterations which take place in the confused heap of co-existing psychic
states. But that is a change of quality rather than of magnitude.

What makes hope such an intense pleasure is the fact
that the future, which we dispose of to our liking, appears to us at the
same time under a multitude of forms, equally attractive and equally

(10) possible. Even if the most coveted of these becomes
realized, it will be necessary to give up the others, and we shall have
lost a great deal. The idea of the future, pregnant with an infinity of
possibilities, is thus more fruitful than the future itself, and this is
why we find more charm in hope than in possession, in dreams than in
reality.

The emotions of joy and
sorrow. Their successive stages correspond to qualitative changes in the
whole of our psychic states

Let us try to discover the nature of an increasing
intensity of joy or sorrow in the exceptional cases where no physical
symptom intervenes. Neither inner joy nor passion is an isolated inner
state which at first occupies a corner of the soul and gradually
spreads. At its lowest level it is very like a turning of our states of
consciousness towards the future. Then, as if their weight were
diminished by this attraction, our ideas and sensations succeed one
another with greater rapidity; our movements no longer cost us the same
effort. Finally, in cases of extreme joy, our perceptions and memories
become tinged with an indefinable quality, as with a kind of heat or
light, so novel that now and then, as we stare at our own self, we
wonder how it can really exist. Thus there are several characteristic
forms of purely inward joy, all of which are successive stages
corresponding to qualitative alterations in the whole of our psychic
states. But the number of states which are concerned with each of these
alterations is more or less considerable, and, without explicitly
counting them, we know very

(11) well whether, for example, our joy pervades all the
impressions which we receive in the course of the day or whether any
escape from its influence. We thus set up points of division in the
interval which separates two successive forms of joy, and this gradual
transition from one to the other makes them appear in their turn as
different intensities of one and the same feeling, which is thus
supposed to change in magnitude. It could be easily shown that the
different degrees of sorrow also correspond to qualitative changes.
Sorrow begins by being nothing more than a facing towards the past, an
impoverishment of our sensations and ideas, as if each of them were now
contained entirely in the little which it gives out, as if the future
were in some way stopped up. And it ends with an impression of crushing
failure, the effect of which is that we aspire to nothingness, while
every new misfortune, by making us understand better the uselessness of
the struggle, causes us a bitter pleasure.

The aesthetic feelings.
Their increasing intensities are really different feelings

The aesthetic feelings offer us a still more striking
example of this progressive stepping in of new elements, which can be
detected in the fundamental emotion and which seem to increase its
magnitude, although in reality they do nothing more than alter its
nature. Let us consider the simplest of them, the feeling of grace. At
first it is only the perception of a certain ease, a certain facility in
the outward movements. And as those move-

(12) -ments are easy which prepare the way for others, we
are led to find a superior ease in the movements which can be foreseen,
in the present attitudes in which future attitudes are pointed out and,
as it were, prefigured. If jerky movements are wanting in grace, the
reason is that each of them is self-sufficient and does not announce
those which are to follow. If curves are more graceful than broken
lines, the reason is that, while a curved line changes its direction at
every moment, every new direction is indicated in the preceding one.
Thus the perception of ease in motion passes over into the pleasure of
mastering the flow of time and of holding the future in the present. A
third element comes in when the graceful movements submit to a rhythm
and are accompanied by music. For the rhythm and measure, by allowing us
to foresee to a still greater extent the movements of the dancer, make
us believe that we now control them. As we guess almost the exact
attitude which the dancer is going to take, he seems to obey us when he
really takes it : the regularity of the rhythm establishes a kind of
communication between him and us, and the periodic returns of the
measure are like so many invisible threads by means of which we set in
motion this imaginary puppet. Indeed, if it stops for an instant, our
hand in its impatience cannot refrain from making a
movement, as though to push it, as though to replace it in the
midst of this movement, the rhythm of which has taken complete
possession

(13) of our thought and will. Thus a kind of
physical sympathy enters into the feeling of grace. Now, in analysing
the charm of this sympathy, you will find that it pleases you through
its affinity with moral sympathy, the idea of which it subtly suggests.
This last element, in which the others are merged after having in a
measure ushered it in, explains the irresistible attractiveness of
grace. We could hardly make out why it affords us such pleasure if it
were nothing but a saving of effort, as Spencer maintains.[1] But
the truth is that in anything which we call very graceful we imagine
ourselves able to detect, besides the lightness which is a sign of
mobility, some suggestion of a possible movement towards ourselves, of a
virtual and even nascent sympathy. It is this mobile sympathy, always
ready to offer itself, which is just the essence of higher grace. Thus
the increasing intensities of aesthetic feeling are here resolved into
as many different feelings, each one of which, already heralded by its
predecessor, becomes perceptible in it and then completely eclipses it.
It is this qualitative progress which we interpret as a change of
magnitude, because we like simple thoughts and because our language is
ill-suited to render the subtleties of psychological analysis.

To understand how the feeling of the beautiful itself
admits of degrees, we should have to submit

The feeling of beauty: art
puts to sleep our active and resistant powers and makes us responsive to
suggestion

(14) it to a minute analysis. Perhaps the difficultywhich
we experience in defining it is largely owing to the fact that we look
upon the beauties of nature as anterior to those of art: the processes
of art are thus supposed to be nothing more than means by which the
artist expresses the beautiful, and the essence of the beautiful remains
unexplained. But we might ask ourselves whether nature is beautiful
otherwise than through meeting by chance certain processes of our art,
and whether, in a certain sense, art is not prior to nature. Without
even going so far, it seems more in conformity with the rules of a sound
method to study the beautiful first in the works in which it has been
produced by a conscious effort, and then to pass on by imperceptible
steps from art to nature, which may be looked upon as an artist in its
own way. By placing ourselves at this point of view, we shall perceive
that the object of art is to put to sleep the active or rather resistant
powers of our personality, and thus to bring us into a state of perfect
responsiveness, in which we realize the idea that is suggested to us and
sympathize with the feeling that is expressed. In the processes of art
we shall find, in a weakened form, a refined and in some measure
spiritualized version of the processes commonly used to induce the state
of hypnosis. Thus, in music, the rhythm and measure
suspend the normal flow of our sensations and ideas by causing our
attention to swing to and

(15) fro between fixed points, and they take hold of us
with such force that even the faintest imitation of a groan will suffice
to fill us with the utmost sadness. If musical sounds affect us more
powerfully than the sounds of nature, the reason is that nature confines
itself to expressing feelings, whereas music suggests them
to us. Whence indeed comes the charm of poetry ? The poet is he with
whom feelings develop into images, and the images themselves into words
which translate them while obeying the laws of rhythm. In seeing these
images pass before our eyes we in our turn experience the feeling which
was, so to speak, their emotional equivalent : but we should never
realize these images so strongly without the regular movements of the
rhythm by which our soul is lulled into self-forgetfulness, and, as in a
dream, thinks and sees with the poet. The plastic arts obtain an effect
of the same kind by the fixity which they suddenly impose upon life, and
which a physical contagion carries over to the attention of the
spectator. While the works of ancient sculpture express faint emotions
which play upon them like a passing breath, the pale immobility of the
stone causes the feeling expressed or the movement just begun to appear
as if they were fixed for ever, absorbing our thought and our will in
their own eternity. We find in architecture, in the very
midst of this startling immobility, certain effects analogous to
those of rhythm. The symmetry of form, the indefinite repetition of the
same

(16) architectural motive, causes our faculty of
perception to oscillate between the same and the same again, and gets
rid of those customary incessant changes which in ordinary life bring us
back without ceasing to the consciousness of our personality even the
faint suggestion of an idea will then be enough to make the idea fill
the whole of our mind. Thus art aims at impressing feelings on us rather
than expressing them ; it suggests them to us, and willingly dispenses
with the imitation of nature when it finds some more efficacious means.
Nature, like art, proceeds by suggestion, but does not command the
resources of rhythm. It supplies the deficiency by the long comradeship,
based on influences received in common by nature and by ourselves, of
which the effect is that the slightest indication by nature of a feeling
arouses sympathy in our minds, just as a mere gesture on the part of the
hypnotist is enough to force the intended suggestion upon a subject
accustomed to his control. And this sympathy is shown in particular when
nature displays to us beings of normal proportions,
so that our attention is distributed equally over all the parts of the
figure without being fixed on any one of them our perceptive faculty
then finds itself lulled and soothed by this harmony, and nothing
hinders any longer the free play of sympathy, which is ever ready to
come forward as soon as the obstacle in its path is removed.

It follows from this analysis that the feeling of

Stages in the aesthetic
emotions

(17) the beautiful is no specific feeling, but that
every feeling experienced by us will assume an aesthetic character,
provided that it has been suggested, and
not caused. It will now be understood why
the aesthetic emotion seems to us to admit of degrees of intensity, and
also of degrees of elevation. Sometimes the feeling which is suggested
scarcely makes a break in the compact texture of psychic phenomena of
which our history consists; sometimes it draws our attention from them,
but not so that they become lost to sight ; sometimes, finally, it puts
itself in their place, engrosses us and completely monopolizes our soul.
There are thus distinct phases in the progress of an aesthetic feeling,
as in the state of hypnosis ; and these phases correspond less to
variations of degree than to differences of state or of nature. But the
merit of a work of art is not measured so much by the power with which
the suggested feeling takes hold of us as by the richness of this
feeling itself : in other words, besides degrees of intensity we
instinctively distinguish degrees of depth or elevation. If this last
concept be analysed, it will be seen that the feelings and thoughts
which the artist suggests to us express and sum up a more or less
considerable part of his history. If the art which gives only sensations
is an inferior art, the reason is that analysis often fails to discover
in a sensation anything beyond the sensation itself. But the greater
number of emotions are instinct with a

(18) thousand sensations, feelings or ideas which
pervade them: each one is then a state unique of its kind and
indefinable, and it seems that we should have to re-live the life of the
subject who experiences it if we wished to grasp it in its original
complexity. Yet the artist aims at giving us a share in this emotion, so
rich, so personal, so novel, and at enabling us to experience what he
cannot make us understand. This he will bring about by choosing, among
the outward signs of his emotions, those which our body is likely to
imitate mechanically, though slightly, as soon as it perceives them, so
as to transport us all at once into the indefinable psychological state
which called them forth. Thus will be broken down the barrier interposed
by time and space between his consciousness and ours: and the richer in
ideas and the more pregnant with sensations and emotions is the feeling
within whose limits the artist has brought us, the deeper and the higher
shall we find the beauty thus expressed. The successive intensities of
the aesthetic feeling thus correspond to changes of state occurring in
us, and the degrees of depth to the larger or smaller number of
elementary psychic phenomena which we dimly discern in the fundamental
emotion.

The moral feelings. Pity.
Its increasing intensity is a qualitative progress.

The moral feelings might be studied in the same way. Let
us take pity as an example.It consists in the first place in
putting oneself mentally in the place of others, in suffering their
pain. But if it were

(19) nothing more, as some have maintained, it would
inspire us with the idea of avoiding the wretched rather than helping
them, for pain is naturally abhorrent to us. This feeling of horror may
indeed be at the root of pity; but a new element soon comes in, the need
of helping our fellow-men and of alleviating their suffering. Shall we
say with La Rochefoucauld that this so-called sympathy is a calculation,
" a shrewd insurance against evils to come " ? Perhaps a dread
of some future evil to ourselves does hold a place in our compassion for
other people's evil. These however are but lower forms of pity. True
pity consists not so much in fearing suffering as in desiring it. The
desire is a faint one and we should hardly wish to see it realized ; yet
we form it in spite of ourselves, as if Nature were committing some
great injustice and it were necessary to get rid of all suspicion of
complicity with her. The essence of pity is thus a need for
self-abasement, an aspiration downwards. This painful aspiration
nevertheless has a charm about it, because it raises us in our own
estimation and makes us feel superior to those sensuous goods from which
our thought is temporarily detached. The increasing intensity of pity
thus consists in a qualitative progress, in a transition from repugnance
to fear, from fear to sympathy, and from sympathy itself to humility.

We do not propose to carry this analysis any fur-

Conscious states connected
with external causes or involving physical symptoms

(20) -ther. The psychic states whose intensity we have
just defined are deep-seated states which do not seem to have any close
relation to their external cause or to involve the perception of
muscular contraction. But such states are rare. There is hardly any
passion or desire, any joy or sorrow, which is not accompanied by
physical symptoms; and, where these symptoms occur, they probably count
for something in the estimate of intensities. As for the sensations
properly so called, they are manifestly connected with their external
cause, and though the intensity of the sensation cannot be defined by
the magnitude of its cause, there undoubtedly exists some relation
between these two terms. In some of its manifestations consciousness
even appears to spread outwards, as if intensity were being developed
into extensity, e.g. in the case of muscular effort. Let us face this
last phenomenon at once : we shall thus be transported at a bound to the
opposite extremity of the series of psychic phenomena.

Muscular effort seems at
first sight to be quantitative

If there is a phenomenon which seems to be presented
immediately to consciousness under the form of quantity or at least of
magnitude it is undoubtedly muscular effort. We picture to our minds a
psychic force imprisoned in the soul like the winds in the cave of
Aeolus, and only waiting for an opportunity to burst forth : our will is
supposed to watch over

(21) this force and from time to time to open a passage
for it, regulating the outflow by the effect which it is desired to
produce. If we consider the matter carefully, we shall see that this
somewhat crude conception of effort plays a large part in our belief in
intensive magnitudes. Muscular force, whose sphere of action is space
and which manifests itself in phenomena admitting of measure, seems to
us to have existed previous to its manifestations, but in smaller
volume, and, so to speak, in a compressed state : hence we do not
hesitate to reduce this volume more and more, and finally we believe
that we can understand how a purely psychic state, which does not occupy
space, can nevertheless possess magnitude. Science, too, tends to
strengthen the illusion of common sense with regard to this point. Bain,
for example, declares that " the sensibility accompanying muscular
movement coincides with the outgoing stream of nervous energy :
" [2]it is thus just the
emission of nervous force which consciousness perceives. Wundt also
speaks of a. sensation, central in its origin, accompanying the
voluntary innervation of the muscles, and quotes the example of the
paralytic " who has a very distinct sensation of the force which he
employs in the effort to raise his leg, although it remains
motionless." [3] Most of the

(22) authorities adhere to this opinion, which would be
the unanimous view of positive science were it not that several years
ago Professor William James drew the attention of physiologists to
certain phenomena which had been but little remarked, although they were
very remarkable.

The feeling of effort. We
are conscious not of an expenditure of force but of the resulting
muscular movement

When a paralytic strives to raise his useless limb, he
certainly does not execute this movement, but, with or without his will,
he executes another. Some movement is carried out somewhere : otherwise
there is no sensation of effort.[4] Vulpian had already called
attention to the fact that if a man affected with hemiplegia is told to
clench his paralysed fist, he unconsciously carries out this action with
the fist which is not affected. Ferrier described a still more curious
phenomenon.[5] Stretch out your arm while slightly bending your
forefinger, as if you were going to press the trigger of a pistol;
without moving the finger, without contracting any muscle of the hand,
without producing any apparent movement, you will yet be able to feel
that you are expending energy. On a closer examination, however, you
will perceive that this sensation of effort coincides

(23) with the fixation of the muscles of your chest, that
you keep your glottis closed and actively contract your respiratory
muscles. As soon as respiration resumes its normal course the
consciousness of effort vanishes, unless you really move your finger.
These facts already seemed to show that we are conscious, not of an
expenditure of force, but of the movement of the muscles which results
from it. The new feature in Professor James's investigation is that he
has verified the hypothesis in the case of examples which seemed to
contradict it absolutely. Thus when the external rectus muscle of the
right eye is paralysed, the patient tries in vain to turn his eye
towards the right ; yet objects seem to him to recede towards the right,
and since the act of volition has produced no effect, it follows, said
Helmholtz,[6] that he is conscious of the effort of volition.
But, replies Professor James, no account has been taken of what goes on
in the other eye. This remains covered during the experiments;
nevertheless it moves and there is not much trouble in proving that it
does. It is the movement of the left eye, perceived by consciousness,
which produces the sensation of effort together with the impression that
the objects perceived by the right eye are moving. These and similar
observations lead Professor James to assert that the feeling

(24) of effort is centripetal and not centrifugal. We are
not conscious of a force which we are supposed to launch upon our
organism : our feeling of muscular energy at work " is a complex
afferent sensation, which comes from contracted muscles, stretched
ligaments, compressed joints, an immobilized chest, a closed glottis, a
knit brow, clenched jaws," in a word, from all the points of the
periphery where the effort causes an alteration.

Intensity of feeling or
effort proportional to extent of our body affected

It is not for us to take a side in the dispute. After all,
the question with which we have to deal is not whether the feeling of
effort comes from the centre or the periphery but in what does our
perception of its boar affected. intensity exactly consist ? Now, it is
sufficient to observe oneself attentively to reach a conclusion on this
point which Professor James has not formulated, but which seems to us
quite in accord with the spirit of his teaching. We maintain that the
more a given effort seems to us to increase, the greater is the number
of muscles which contract in sympathy with it, and that the apparent
consciousness of a greater intensity of effort at a given point of the
organism is reducible, in reality, to the perception of a larger surface
of the body being affected.

Try, for example, to clench the fist with increasing force. You will
have the impression of a sensation of effort entirely localized in your
hand and running up a scale of magnitudes. In reality, what you
experience in your hand

Our consciousness of an
increase of muscular effort consists in the perception of (1) a great
number of peripheral sensations (2) a qualitative change in some of
them.

(25) remains the same, but the sensation which was at
first localized there has affected your arm and ascended to the
shoulder; finally, the other arm stiffens, both legs do the same, the
respiration is checked; it is the whole body which is at work. But you
fail to notice distinctly all these concomitant movements unless you are
warned of them: till then you thought you were dealing with a single
state of consciousness which changed in magnitude. When you press your
lips more and more tightly against one another, you believe that you are
experiencing in your lips one and the same sensation which is
continually increasing in strength : here again further reflection will
show you that this sensation remains identical, but that certain muscles
of the face and the head and then of all the rest of the body have taken
part in the operation. You felt this gradual encroachment, this increase
of the surface affected, which is in truth a change of quantity ; but,
as your attention was concentrated on your closed lips, you localized
the increase there and you made the psychic force there expended into a
magnitude, although it possessed no extensity. Examine carefully
somebody who is lifting heavier and heavier weights : the muscular
contraction gradually spreads over his whole body. As for the special
sensation which he experiences in the arm which is at work, it remains
constant for a very long time and hardly changes except in

(26) quality, the weight becoming at a certain moment
fatigue, and the fatigue pain. Yet the subject will imagine that he is
conscious of a continual increase in the psychic force flowing into his
arm. He will not recognize his mistake unless he is warned of it, so
inclined is he to measure a given psychic state by the conscious
movements which accompany it! From these facts and from many others of
the same kind we believe we can deduce the following conclusion : our
consciousness of an increase of muscular effort is reducible to the
twofold perception of a greater number of peripheral sensations, and of
a qualitative change occurring in some of them.

The same definition of
intensity applies to superficial efforts, deep-seated feelings and
states intermediate between the two

We are thus led to define the intensity of a superficial
effort in the same way as that of a deep-seated psychic feeling. In both
cases there is a qualitative progress and an increasing complexity,
indistinctly perceived. But consciousness, accustomed to think in terms
of space and to translate its thoughts into words, will denote the
feeling by a single word and will localize the effort at the exact point
where it yields a useful result : it will then become aware of an effort
which is always of the same nature and increases at the spot assigned to
it, and a feeling which, retaining the same name, grows without changing
its nature. Now, the same illusion of consciousness is likely to be met
with again in the case of the states which are inter-

(27) mediate between superficial efforts and deep-seated
feelings. A large number of psychic states are accompanied, in fact, by
muscular contractions and peripheral sensations. Sometimes these
superficial elements are co-ordinated by a purely speculative idea,
sometimes by an idea of a practical order. In the first case there is
intellectual effort or attention ; in the second we have the emotions
which maybe called violent or acute: anger, terror, and certain
varieties of joy, sorrow, passion and desire. Let us show briefly that
the same definition of intensity applies to these intermediate states.

The intermediate states.
Attention and its relation to muscular contraction

Attention is not a purely physiological phenomenon, but we
cannot deny that it is accompanied by movements. These movements are
neither the cause nor the result of the its relation to phenomenon ;
they are part of it, they express it in terms of space, as Ribot has so
remarkably proved.[6] Fechner had already reduced the effort of
attention in a sense-organ to the muscular feeling " produced by
putting in motion, by a sort of reflex action, the muscles which are
correlated with the different sense organs." He had noticed the
very distinct sensation of tension and contraction of the scalp, the
pressure from without inwards over the whole skull, which we experience
when we make a great effort to recall something. Ribot has studied

(28) more closely the movements which are
characteristic of voluntary attention. " Attention contracts the
frontal muscle : this muscle . . . draws the eyebrow towards itself,
raises it and causes transverse wrinkles on the forehead . . . . In
extreme cases the mouth is opened wide. With children and with many
adults eager attention gives rise to a protrusion of the lips, a kind of
pout." Certainly, a purely psychic factor will always enter into
voluntary attention, even if it be nothing more than the exclusion by
the will of all ideas foreign to the one with which the subject wishes
to occupy himself. But, once this exclusion is made, we believe that we
are still conscious of a growing tension of soul, of an immaterial
effort which increases. Analyse this impression and you will find
nothing but the feeling of a muscular contraction which spreads over a
wider surface or changes its nature, so that the tension becomes
pressure, fatigue and pain.

The intensity of violent
emotions as muscular tension

Now, we do not see any essential difference between the
effort of attention and what may be called the effort of psychic
tension: acute desire, uncontrolled anger, passionate love, violent
hatred. Each of these states may be reduced, we believe, to a system of
muscular contractions co-ordinated by an idea ; but in the case of
attention, it is the more or less reflective idea of knowing ; in the
case of emotion, the unreflective idea of acting. The intensity of these
violent emotions is thus likely to be nothing but

(29) the muscular tension which accompanies them. Darwin
has given a remarkable description of the physiological symptoms of
rage. " The action of the heart is much accelerated . . . . The
face reddens or may turn deadly pale. The respiration is laboured, the
chest heaves, and the dilated nostrils quiver. The whole body often
trembles. The voice is affected. The teeth are clenched or ground
together and the muscular system is commonly stimulated to violent,
almost frantic action. The gestures . . . represent more or less plainly
the act of striking or fighting with an enemy." [7]
We shall not go so fax as to maintain, with Professor James,[8]
that the emotion of rage is reducible to the sum of these organic
sensations : there will always be an irreducible psychic element in
anger, if this be only the idea of striking or fighting, of which Darwin
speaks, and which gives a common direction to so many diverse movements.
But, though this idea determines the direction of the emotional state
and the accompanying movements, the growing intensity of the state
itself is, we believe, nothing but the deeper and deeper disturbance of
the organism, a disturbance which consciousness has no difficulty in
measuring by the number and extent of the bodily surfaces concerned. It
will be useless to assert that there is a restrained rage which is all
the more intense. The reason is that, where emotion has free play,
consciousness does not

(30) dwell on the details of the accompanying movements,
but it does dwell upon them and is concentrated upon them when its
object is to conceal them. Eliminate, in short, all trace of organic
disturbance, all tendency towards muscular contraction, and all that
will be left of anger will be the idea, or, if you still insist on
making it an emotion, you will be unable to assign it any intensity.

Intensity and reflex
movements. No essential difference between intensity of deep-seated
feelings and that of violent emotions.

Fear, when strong," says Herbert Spencer,
" expresses itself in cries, in efforts to escape, in palpitations,
in tremblings."[9] We go further, and maintain that these
movements form part of the terror itself : by their means the terror
becomes an emotion capable of passing through different degrees of
intensity. Suppress them entirely, and the more or less intense state of
terror will be succeeded by an idea of terror, the wholly intellectual
representation of a danger which it concerns us to avoid. There are also
high degrees of joy and sorrow, of desire, aversion and even shame, the
height of which will be found to be nothing but the reflex movements
begun by the organism and perceived by consciousness. " When lovers
meet," says Darwin, " we know that their hearts beat quickly,
their breathing is hurried and their faces flushed."[10]
Aversion is marked by movements of repugnance which we repeat without
noticing when we think of the

(31) object of our dislike. We blush and involuntarily
clench the fingers when we feel shame, even if it be retrospective. The
acuteness of these emotions is estimated by the number and nature of the
peripheral sensations which accompany them. Little by little, and in
proportion as the emotional state loses its violence and gains in depth,
the peripheral sensations will give place to inner it will be no longer
our outward movements but our ideas, our memories, our states of
consciousness of every description, which will turn in larger or smaller
numbers in a definite direction. There is, then, no essential difference
from the point of view of intensity between the deep-seated feelings, of
which we spoke at the beginning, and the acute or violent emotions which
we have just passed in review. To say that love, hatred, desire,
increase in violence is to assert that they are projected outwards, that
they radiate to the surface, that peripheral sensations are substituted
for inner states : but superficial or deep-seated, violent or
reflective, the intensity of these feelings always consists in the
multiplicity of simple states which consciousness dimly discerns in
them.

Magnitude of sensations.
Affective and representative sensations.

We have hitherto confined ourselves to feelings and
efforts, complex states the intensity of which does not absolutely
depend on an external cause. But sensations seem to us simple in what
will their magnitude

(32)consist ? The intensity of sensations varies with the
external cause of which they are said to be the conscious equivalent :
how shall we explain the presence of quantity in an effect which is
inextensive, and in this case indivisible? To answer this question, we
must first distinguish between the so-called affective and the
representative sensations. There is no doubt that we pass gradually from
the one to the other and that some affective element enters into the
majority of our simple representations. But nothing prevents us from
isolating this element and inquiring separately, in what does the
intensity of an affective sensation, a pleasure or a pain, consist ?

Affective sensations and
organic disturbances

Perhaps the difficulty of the latter problem is
principally due to the fact that we are unwilling to see in the
affective state anything but the conscious expression of an organic
disturbance, the inward echo of an outward cause. We notice that a more
intense sensation generally corresponds to a greater nervous disturbance
; but inasmuch as these disturbances are unconscious as movements, since
they come before consciousness in the guise of a sensation which has no
resemblance at all to motion, we do not see how they could transmit to
the sensation anything of their own magnitude. For there is nothing in
common, we repeat, between superposable magnitudes such as, for
example, vibration amplitudes, and sensations which do not occupy

(33) space. If the more intense sensation seems to us to
contain the less intense, if it assumes for us, like the physical
impression itself, the form of a magnitude, the reason probably is that
it retains something of the physical impression to which it corresponds.
And it will retain nothing of it if it is merely the conscious
translation of a movement of molecules ; for, just because this movement
is translated into the sensation of pleasure or pain, it remains
unconscious as molecular movement.

Pleasure and pain as signs
of the future reaction rather than psychic translations of the past
stimulus

But it might be asked whether pleasure and pain, instead
of expressing only what has just occurred, or what is actually
occurring, in the organism, as is usually believed, could not also point
out what is going to, or what is tending to take place. It seems indeed
somewhat improbable that nature, so profoundly utilitarian, should have
here assigned to consciousness the merely scientific task of informing
us about the past or the present, which no longer depend upon us. It
must be noticed in addition that we rise by imperceptible stages from
automatic to free movements, and that the latter differ from the former
principally in introducing an affective sensation between the external
action which occasions them and the volitional reaction which ensues.
Indeed, all our actions might have been automatic, and we can surmise
that there are many organized beings iii whose case an external
stimulus causes a definite reaction without calling up consciousness as
an

(34) intermediate agent. If pleasure and pain make their
appearance in certain privileged beings, it is probably to call forth a
resistance to the automatic reaction which would have taken place:
either sensation has nothing to do, or it is nascent freedom. But how
would it enable us to resist the reaction which is in preparation if it
did not acquaint us with the nature of the latter by some definite sign
? And what can this sign be except the sketching, and, as it were, the
prefiguring of the future automatic movements in the very midst of the
sensation which is being experienced ? The affective state must then
correspond not merely to the physical disturbances, movements or
phenomena which have taken place, but also, and especially, to those
which are in preparation, those which are getting ready to be.

Intensity of affective
sensations would then be our consciousness of involuntary movements
tending to follow the stimulus

It is certainly not obvious at first sight how this
hypothesis simplifies the problem. For we are trying to find what there
can be in common, from the point of view of magnitude, between a
physical phenomenonand a state of consciousness, and we seem to
have merely turned the difficulty round by making the present state of
consciousness a sign of the future reaction, rather than a psychic
translation of the past stimulus. But the difference between the two
hypotheses is considerable. For the molecular
disturbances which were mentioned just now are necessarily
unconscious, since no trace of the movements

(35) themselves can be actually perceived in the sensation
which translates them. But the automatic movements which tend to follow
the stimulus as its natural outcome are likely to be conscious as
movements: or else the sensation itself, whose function is to invite us
to choose between this automatic reaction and other possible movements,
would be of no avail. The intensity of affective sensations might thus
be nothing more than our consciousness of the involuntary movements
which are being begun and outlined, so to speak, within these states,
and which would have gone on in their own way if nature had made us
automata instead of conscious beings.

Intensity of a pain
estimated by extent of organism affected

If such be the case, we shall not compare a pain of
increasing intensity to a note which grows louder and louder, but rather
to a symphony, in which an increasing number of instruments make
themselvesheard. Within the
characteristic sensation, which gives the tone to all the others,
consciousness distinguishes a larger or smaller number of sensations
arising at different points of the periphery, muscular contractions,
organic movements of every kind: the choir of these elementary psychic
states voices the new demands of the organism, when confronted by a new
situation. In other words, we estimate the intensity of a pain by the
larger or smaller part of the organism which takes interest in it.
Richet[11]

(36) has observed that the slighter the pain, the more
precisely is it referred to a particular spot ; if it becomes more
intense, it is referred to the whole of the member affected. And he
concludes by saying that " the pain spreads in proportion as it is
more intense."[12] We should rather reverse the sentence,
and define the intensity of the pain by the very number and extent of
the parts of the body which sympathize with it and react, and whose
reactions are perceived by consciousness. To convince ourselves of this,
it will be enough to read the remarkable description of disgust given by
the same author: " If the stimulus is slight there may be neither
nausea nor vomiting . . . . If the stimulus is stronger, instead of
being confined to the pneumo-gastric nerve, it spreads and affects
almost the whole organic system. The face turns pale, the smooth muscles
of the skin contract, the skin is covered with a cold perspiration, the
heart stops beating in a word there is a general organic disturbance
following the stimulation of the medulla oblongata, and this disturbance
is the supreme expression of disgust."[13] But is it nothing
more than its expression ? In what will the general sensation of disgust
consist, if not in the sum of these elementary sensations ? And what can
we understand here by increasing intensity, if it is not the constantly
increasing number of sensations

(37)which join in with the sensations already experienced
? Darwin has drawn a striking picture of the reactions following a pain
which becomes more and more acute. "Great pain urges all animals .
. . to make the most violent and diversified efforts to escape from the
cause of suffering . . . . With men the mouth may be closely compressed,
or more commonly the lips are retracted with the teeth clenched or
ground together . . . . The eyes stare wildly . . . or the brows are
heavily contracted. Perspiration bathes the body . . . . The circulation
and respiration are much affected."[14] Now, is it not by
this very contraction of the muscles affected that we measure the
intensity of a pain ? Analyse your idea of any suffering which you call
extreme : do you not mean that it is unbearable, that is to say, that it
urges the organism to a thousand different actions in order to escape
from it ? I can picture to myself a nerve transmitting a pain which is
independent of all automatic reaction ; and I can equally understand
that stronger or weaker stimulations influence this nerve differently.
But I do not see how these differences of sensation would be interpreted
by our consciousness as differences of quantity unless we connected them
with the reactions which usually accompany them, and which are more or
less extended and more or

(38) less important. Without these subsequent reactions,
the intensity of the pain would be a quality, and not a magnitude.

Pleasure compared by bodily
inclination

We have hardly any other means of comparing several
pleasures with one another. What do we mean by a greater pleasure except
a pleasure that is preferred ? And what can our preference be, except a
certain disposition of our organs, the effect of which is that, when two
pleasures are offered simultaneously to our mind, our body inclines
towards one of them ? Analyse this inclination itself and you will find
a great many little movements which begin and become perceptible in the
organs concerned, and even in the rest of the body, as if the organism
were coming forth to meet the pleasure as soon as it is pictured. When
we define inclination as a movement, we are not using a metaphor. When
confronted by several pleasures pictured by our mind, our body turns
towards one of them spontaneously, as though by a reflex action. It
rests with us to check it, but the attraction of the pleasure is nothing
but this movement that is begun, and the very keenness of the pleasure,
while we enjoy it, is merely the inertia of the organism, which is
immersed in it and rejects every other sensation. Without this vis inertiae
of which we become conscious by the very resistance
which we offer to anything that might distract us, pleasure would
be a state, but no longer a magnitude. In the moral as in

(39) the physical world, attraction serves to define
movement rather than to produce it.

The intensity of
representative sensations. Many also affective and intensity is measured
by reaction called forth. In others a new element enters

We have studied the affective sensations separately, but
we must now notice that many representative sensations possess an
affective character, and thus call forth a reaction on our part which we
take into account in estimating their intensity. A considerable increase
of light is represented for us by a characteristic sensation which is
not yet pain, but which is analogous to dazzling. In proportion as the
amplitude of sound-vibrations increases, our head and then our body seem
to us to vibrate or to receive a shock. Certain representative
sensations, those of taste, smell and temperature, have a fixed
character of pleasantness or unpleasantness. Between flavours which are
more or less bitter you will hardly distinguish anything but differences
of quality; they are like different shades of one and the same colour.
But these differences of quality are at once interpreted as differences
of quantity, because of their affective character and the more or less
pronounced movements of reaction, pleasure or repugnance, which they
suggest to us. Besides, even when the sensation remains purely
representative, its external cause cannot exceed a certain degree of
strength or weakness without inciting us to movements which enable us to
measure it. Sometimes indeed

(40) we have to make an effort to perceive this
sensation, as if it were trying to escape notice ; sometimes on the
other hand it obsesses us, forces itself upon us and engrosses us to
such an extent that we make every effort to escape from it and to remain
ourselves. In the former case the sensation is said to be of slight
intensity, and in the latter case very intense. Thus, in order to
perceive a distant sound, to distinguish what we call a faint smell or a
dim light, we strain all our faculties, we " pay attention."
And it is just because the smell and the light thus require to be
reinforced by our efforts that they seem to us feeble. And, inversely,
we recognize a sensation of extreme intensity by the irresistible reflex
movements to which it incites us, or by the powerlessness with which it
affects us. When a cannon is fired off close to our ears or a dazzling
light suddenly flares up, we lose for an instant the consciousness of
our personality ; this state may even last some time in the case of a
very nervous subject. It must be added that, even within the range of
the so-called medium intensities, when we are dealing on even terms with
a representative sensation, we often estimate its importance by
comparing it with another which it drives away, or by taking account of
the persistence with which it returns. Thus the ticking of a watch seems
louder at night because it easily monopolizes a consciousness almost
empty of sensations and ideas. Foreigners talking to one

(41) another in a language which we do not understand seem
to us to speak very loudly, because their words no longer call up any
ideas in our mind, and thus break in upon a kind of intellectual silence
and monopolize our attention like the ticking of a watch at night. With
these so-called medium sensations, however, we approach a series of
psychic states, the intensity of which is likely to possess a new
meaning. For, in most cases, the organism hardly reacts at all, at least
in a way that can be perceived ; and yet we still make a magnitude out
of the pitch of a sound, the intensity of a light, the saturation of a
colour. Doubtless, a closer observation of what takes place in the whole
of the organism when we hear such and such a note or perceive such and
such a colour has more than one surprise in store for us. Has not C.
Féré shown that every sensation is accompanied by an increase in
muscular force which can be measured by the dynamometer?[15] But
of an increase of this kind there is hardly any consciousness at all,
and if we reflect on the precision with which we distinguish sounds and
colours, nay, even weights and temperatures, we shall easily guess that
some new element must come into play in our estimate of them.

Now, the nature of this element is easy to deter-

The purely representative
sensations are measured by their external causes

(42) -mine. For, in proportion as a sensation loses its
affective character and becomes representative the reactions which it
called forth on our part tend to disappear, but at the same time we
perceive the external object which is its cause, or if we do not now
perceive it, we have perceived it, and we think of it. Now, this cause
is extensive and therefore measurable : a constant experience, which
began with the first glimmerings of consciousness and which continues
throughout the whole of our life, shows us a definite shade of sensation
corresponding to a definite amount of stimulation. We thus associate the
idea of a certain quantity of cause with a certain quality of effect ;
and finally, as happens in the case of every acquired perception, we
transfer the idea into the sensation, the quantity of the cause into the
quality of the effect. At this very moment the intensity, which was
nothing but a certain shade or quality of the sensation, becomes a
magnitude. We shall easily understand this process if, for example, we
hold a pin in our right hand and prick our left hand more and more
deeply. At first we shall feel as it were a tickling, then a touch which
is succeeded by a prick, then a pain localized at a point, and finally
the spreading of this pain over the surrounding zone. And the more we
reflect on it, the more clearly shall we see that we are here dealing
with so many qualitatively distinct sensations,

(43) so many varieties of a single species. But yet we
spoke at first of one and the same sensation which spread further and
further, of one prick which increased in intensity. The reason is that,
without noticing it, we localized in the sensation of the left hand,
which is pricked, the progressive effort of the right hand, which
pricks. We thus introduced the cause into the effect, and unconsciously
interpreted quality as quantity, intensity as magnitude. Now, it is easy
to see that the intensity of every representative sensation ought to be
understood in the same way.

The sensations of sound.
Intensity measured by effort necessary to produce similar sound

The sensations of sound display well marked degrees of
intensity. We have already spoken of the necessity of taking into
account the affective character of these sensations, the shock received
by the whole of the organism. We have shown that a very intense sound is
one which engrosses our attention, which supplants all the others. But
take away the shock, the well-marked vibration, which you sometimes feel
in your head or even throughout your body take away the clash which
takes place between sounds heard simultaneously: what will be left
except an indefinable quality of the sound which is heard ? But this
quality is immediately interpreted as quantity because you have obtained
at yourself a thousand times, e.g. by striking some object and thus
expending a definite quantity of effort. You know, too, how far you
would

(44) have to raise your voice to produce a similar sound,
and the idea of this effort immediately comes into your mind when you
transform the intensity of the sound into a magnitude. Wundt[16]
has drawn attention to the quite special connexions of vocal and
auditory nervous filaments which are met with in the human brain. And
has it not been said that to hear is to speak to oneself ? Some
neuropaths cannot be present at a conversation without moving their lips
; this is only an exaggeration of what takes place in the case of every
one of us. How will the expressive or rather suggestive power of music
be explained, if not by admitting that we repeat to ourselves the sounds
heard, so as to carry ourselves back into the psychic state out of which
they emerged, an original state, which nothing will express, but which
something may suggest, viz., the very motion and attitude which the
sound imparts to our body ?

Intensity and pitch. The
part played by muscular effort

Thus, when we speak of the intensity of a sound of medium
force as a magnitude, we allude principally to the greater or less
effort which we should have ourselves to expend in order to summon, by
our own effort, the same auditory
sensation. Now, besides the intensity, we distinguish another
characteristic property of the sound, its pitch.

(45) Are the differences in pitch, such as our ear
perceives, quantitative differences ? I grant that a sharper sound calls
up the picture of a higher position in space. But does it follow from
this that the notes of the scale, as auditory sensations, differ
otherwise than in quality? Forget what you have learnt from physics,
examine carefully your idea of a higher or lower note, and see whether
you do not think simply of the greater or less effort which the tensor
muscle of your vocal chords has to make in order to produce the note ?
As the effort by which your voice passes from one note to another is
discontinuous, you picture to yourself these successive notes as points
in space, to be reached by a series of sudden jumps, in each of which
you cross an empty separating interval: this is why you establish
intervals between the notes of the scale. Now, why is the line along
which we dispose them vertical rather than horizontal, and why do we say
that the sound ascends in some cases and descends in others? It must be
remembered that the high notes seem to us to produce some sort of
resonance in the head and the deep notes in the thorax : this
perception, whether real or illusory, has undoubtedly had some effect in
making us reckon the intervals vertically. But we must also notice that
the greater the tension of the vocal chords in the chest voice, the
greater is the surface of the body affected, if the singer is
inexperienced ; this is just the reason why the

(46) effort is felt by him as more intense. And as he
breathes out the air upwards, he will attribute the same direction to
the sound produced by the current of air; hence the sympathy of a larger
part of the body with the vocal muscles will be represented by a
movement upwards. We shall thus say that the note is higher because the
body makes an effort as though to reach an object which is more elevated
in space. In this way it became customary to assign a certain height to
each note of the scale, and as soon as the physicist was able to define
it by the number of vibrations in a given time to which it corresponds,
we no longer hesitated to declare that our ear perceived differences of
quantity directly. But the sound would remain a pure quality if we did
not bring in the muscular effort which produces it or the vibrations
which explain it.

The sensations of heat and
cold. Those soon become affective and are measured by reactions called
forth

The experiments of Blix, Goldscheider and Donaldson[17]
have shown that the points on the surface of the body which feel cold
are not the same as those which feel heat. Physiology is thus disposed
to set up a distinction of nature, and not merely of degree, between the
sensations of heat and cold. But psychological observation goes further,
for close attention can easily discover specific differences between the
different sensations of heat, as also between the sensations of

(47) cold. A more intense heat is really another kind of
heat. We call it more intense because we have experienced this same
change a thousand times when we approached nearer and nearer a source of
heat, or when a growing surface of our body was affected by it. Besides,
the sensations of heat and cold very quickly become affective and incite
us to more or less marked reactions by which we measure their external
cause : hence, we are inclined to set up similar quantitative
differences among the sensations which correspond to lower intensities
of the cause. But I shall not insist any further; every one must
question himself carefully on this point, after making a clean sweep of
everything which his past experience has taught him about the cause of
his sensations and coming face to face with the sensations themselves.
The result of this examination is likely to be as follows it will be
perceived that the magnitude of a representative sensation depends on
the cause having been put into the effect, while the intensity of the
affective element depends on the more or less important reactions which
prolong the external stimulations and find their way into the sensation
itself.

The sensation of pressure
and weight measured by extent of the organism affected

The same thing will be experienced in the case of pressure
and even weight. When you say that a pressure on your hand becomes
stronger and stronger, see whether you do not mean that there first was
a contact, then a pressure, afterwards a

(48) pain, and that this pain itself, after having gone
through a series of qualitative changes, has spread further and further
over the surrounding region. Look again and see whether you do not bring
in the more and more intense, i.e. more and more extended, effort of
resistance which you oppose to the external pressure. When the
psychophysicist lifts a heavier weight, he experiences, he says, an
increase of sensation. Examine whether this increase of sensation ought
not rather to be called a sensation of increase. The whole question is
centred in this, for in the first case the sensation would be a quantity
like its external cause, whilst in the second it would be a quality
which had become representative of the magnitude of its cause. The
distinction between the heavy and the light may seem to be as
old-fashioned and as childish as that between the hot and the cold. But
the very childishness of this distinction makes it a psychological
reality. And not only do the heavy and the light impress our
consciousness as generically different, but the various degrees of
lightness and heaviness are so many species of these two genera. It must
be added that the difference of quality is here translated spontaneously
into a difference of quantity, because of the more or less extended
effort which our body makes in order to lift a given weight. Of this you
will soon become aware if you are asked to lift a basket which, you are
told, is full of scrap-iron, whilst in fact there is nothing in it. You
will think you

(49) are losing your balance when you catch hold of it, as
though distant muscles had interested themselves beforehand in the
operation and experienced a sudden disappointment. It is chiefly by the
number and nature of these sympathetic efforts, which take place at
different points of the organism, that you measure the sensation of
weight at a given point ; and this sensation would be nothing more than
a quality if you did not thus introduce into it the idea of a magnitude.
What strengthens the illusion on this point is that we have become
accustomed to believe in the immediate perception of a homogeneous
movement in a homogeneous space. When I lift a light weight with my arm,
all the rest of my body remaining motionless, I experience a series of
muscular sensations each of which has its " local sign," its
peculiar shade : it is this series which my consciousness interprets as
a continuous movement in space. If I afterwards lift a heavier weight to
the same height with the same speed, I pass through a new series of
muscular sensations, each of which differs from the corresponding term
of the preceding series. Of this I could easily convince myself by
examining them closely. But as I interpret this new series also as a
continuous movement, and as this movement has the same direction, the
same duration and the same velocity as the preceding, my consciousness
feels itself bound to localize the difference between the second series
of sensations and the first elsewhere than in the

(50) movement itself. It thus materializes this difference
at the extremity of the arm which moves ; it persuades itself that the
sensation of movement has been identical in both cases, while the
sensation of weight differed in magnitude. But movement and weight axe
but distinctions of the reflective consciousness : what is present to
consciousness immediately is the sensation of, so to speak, a heavy
movement, and this sensation itself can be resolved by analysis into a
series of muscular sensations, each of which represents by its shade its
place of origin and by its colour the magnitude of the weight lifted.

The sensation of light.
Qualitative changes of colour interpreted as quantitative changes in
intensity of luminous source.

Shall we call the intensity of light a quantity, or shall
we treat it as a quality ? It has not perhaps been sufficiently noticed
what a large number of different factors co-operate in daily life in
giving us information about the nature of the luminous source. We know
from long experience that, when we have a difficulty in distinguishing
the outlines and details of objects, the light is at a distance or on
the point of going out.Experience has taught us that the affective
sensation or nascent dazzling that we experience in certain cases must
be attributed to a higher intensity of the cause. Any increase or
diminution in the number of luminous sources alters the way in which
the. sharp lines of bodies stand out and also the shadows which they
project. Still more important are the changes of hue which coloured

(51) surfaces, and even the pure colours of the spectrum,
undergo under the influence of a brighter or dimmer light. As the
luminous source is brought nearer, violet takes a bluish tinge, green
tends to become a whitish yellow, and red a brilliant yellow. Inversely,
when the light is moved away, ultramarine passes into violet and yellow
into green; finally, red, green and violet tend to become a whitish
yellow. Physicists have remarked these changes of hue for some time;[18]
but what is still more remarkable is that the majority of men do not
perceive them, unless they pay attention to them or are warned of them.
Having made up our mind, once for all, to interpret changes of quality
as changes of quantity, we begin by asserting that every object has its
own peculiar colour, definite and invariable. And when the hue of
objects tends to become yellow or blue, instead of saying that we see
their colour change under the influence of an increase or diminution of
light, we assert that the colour remains the same but that our sensation
of luminous intensity increases or diminishes. We thus substitute once
more, for the qualitative impression received by our consciousness, the
quantitative interpretation given by our understanding. Helmholtz has
described a case of interpretation of the same kind, but still more
complicated: " If we form white with two colours of the spectrum,
and if we increase or

(52) diminish the intensities of the two coloured lights
in the same ratio, so that the proportions of the combination remain the
same, the resultant colour remains the same although the relative
intensity of the sensations undergoes a marked change . . . . This
depends on the fact that the light of the sun, which we consider as the
normal white light during the day, itself undergoes similar
modifications of shade when the luminous intensity varies."[19]

Does experiment prove that
we can measure directly our sensations of light?

But yet, if we often judge of variations in the luminous
source by the relative changes of hue of the objects which surround us,
this is no longer the case in simple instances where a single object,
e.g. a white surface, passes successively through different degrees of
luminosity. We axe bound to insist particularly on this last point. For
the physicist speaks of degrees of luminous intensity as of real
quantities : and, in fact, he measures them by the photometer. The
psychophysicist goes still further : he maintains that our eye itself
estimates the intensities of light. Experiments have been attempted, at
first by Delboeuf,[20] and afterwards by Lehmann and Neiglick,[21]
with

(53) the view of constructing a psychophysical formula
from the direct measurement of our luminous sensations. Of these
experiments we shall not dispute the result, nor shall we deny the value
of photometric processes ; but we must see how we have to interpret
them.

Photometric experiments. We
perceive different shades and afterwards interpret them as decreasing
intensities of white light

Look closely at a sheet of paper lighted e.g. by four
candles, and put out in succession one, two, three of them. You say that
the surface remains white and that its brightness diminishes. But you
are aware that one candle has just been put out ; or, if you do not know
it, you have often observed a similar change in the appearance of a
white surface when the illumination was diminished. Put aside what you
remember of your past experiences and what you are accustomed to say of
the present ones ; you will find that what you really perceive is not a
diminished illumination of the white surface, it is a layer
o f shadow passing over this surface at the moment the candle
is extinguished. This shadow is a reality to your consciousness, like
the light itself. If you call the first surface in all its brilliancy
white, you will have to give another name to what you now see, for it is
a different thing : it is, if we may say so, a new shade of white. We
have grown accustomed, through the combined influence of our past
experience and of physical theories, to regard black as the absence, or
at least as the minimum, of luminous sensation, and the succes-

(54) -sive shades of grey as decreasing intensities of
white light. But, in point of fact, black has just as much reality for
our consciousness as white, and the decreasing intensities of white
light illuminating a given surface would appear to an unprejudiced
consciousness as so many different shades, not unlike the various
colours of the spectrum. This is the reason why the change in the
sensation is not continuous, as it is in the external cause, and why the
light can increase or decrease for a certain period without producing
any apparent change in the illumination of our white surface the
illumination will not appear to change until the increase or decrease of
the external light is sufficient to produce a new quality. The
variations in brightness of a given colour-the affective sensations of
which we have spoken above being left aside-would thus be nothing but
qualitative changes, were it not our custom to transfer the cause to the
effect and to replace our immediate impressions by what we learn from
experience and science. The same thing might be said of degrees of
saturation. Indeed, if the different intensities of a colour correspond
to so many different shades existing between this colour and black, the
degrees of saturation are like shades intermediate between this same
colour and pure white. Every colour, we might say, can be regarded under
two aspects, from the point of view of black and from the
point of view of white. And black is then to intensity what white is to
saturation.

(55)

In photometric experiments the physicist compares,
not sensations, but physical effects

The meaning of the photometric experiments will now be understood. A
candle placed at a certain distance from a sheet of paper illuminates it
in a certain way: you double the distance and find that four candles are
required to produce the same sensation. From this you conclude that if
you had doubled the distance without increasing the intensity of the
luminous source, the result ant illumination would have been only
one-fourth as bright. But it is quite obvious that you are here dealing
with the physical and not the psychological effect. For it cannot be
said that you have compared two sensations with one another you have
made use of a single sensation in order to compare two different
luminous sources with each other, the second four times as strong as the
first but twice as far off. In a word, the physicist never brings in
sensations which are twice or three times as great as others, but only
identical sensations, destined to serve as intermediaries between two
physical quantities which can then be equated with one another. The
sensation of light here plays the part of the auxiliary unknown quantity
which the mathematician introduces into his calculations, and which is
not intended to appear in the final result.

But the object of the psychophysicist is entirely different
: it is the sensation of light itself which he studies, and claims to
measure. Sometimes he will proceed to integrate infinitely small

The psychophysicist claims
to compare and measure sensations. Delboeuf's experiments

(56) differences, after the method of Fechner ; sometimes
he will compare one sensation directly with another. The latter method,
due to Plateau and Delboeuf, differs far less than has hitherto been
believed from Fechner's : but, as it bears more especially on the
luminous sensations, we shall deal with it first. Delboeuf places an
observer in front of three concentric rings which vary in brightness. By
an ingenious arrangement he can cause each of these rings to pass
through all the shades intermediate between white and black. Let us
suppose that two hues of grey are simultaneously produced on two of the
rings and kept unchanged ; let us call them A and B. Delboeuf alters the
brightness, C, of the third ring, and asks the observer to tell him
whether, at a certain moment, the grey, B, appears to him equally
distant from the other two. A moment comes, in fact, when the observer
states that the contrast A B is equal to the contrast B C, so that,
according to Delboeuf, a scale of luminous intensities could be
constructed on which we might pass from each sensation to the following
one by equal sensible contrasts : our sensations would thus be measured
by one another. I shall not follow Delboeuf into the conclusions which
he has drawn from these remarkable experiments : the essential question,
the only question, as it seems to me, is whether a contrast A B,
formed of the elements A and B, is really equal to a contrast B C, which
is differently

(57) composed. As soon as it is proved that two sensations
can be equal without being identical, psychophysics will be established.
But it is this equality which seems to me open to question : it is easy
to explain, in fact, how a sensation of luminous intensity can be said
to be at an equal distance from two others.

In what case differences of
colour might be interpreted as differences in magnitude

Let us assume for a moment that from our birth onwards the
growing intensity of a luminous source had always called up in our
consciousness one after the other, the different colours of the
spectrum. There is no doubt that these colours would then appear to us
as so many notes of a gamut, as higher or lower degrees in a scale, in a
word, as magnitudes. Moreover it would be easy for us to assign each of
them its place in the series. For although the extensive cause varies
continuously, the changes in the sensation of colour are discontinuous,
passing from one shade to another shade. However numerous, then, may be
the shades intermediate between the two colours, A and B, it will always
be possible to count them in thought, at least roughly, and ascertain
whether this number is almost equal to that of the shades which separate
B from another colour C. In the latter case it will be said that B is
equally distant from A and C, that the contrast is the same on one side
as on the other. But this will always be merely a convenient
interpretation : for although the number of intermediate shades may be
equal

(58) on both sides, although we may pass from one to the
other by sudden leaps, we do not know whether these leaps are
magnitudes, still less whether they are equal magnitudes: above
all it would be necessary to show that the intermediaries which have
helped us throughout our measurement could be found again inside the
object which we have measured. If not, it is only by a metaphor that a
sensation can be said to be an equal distance from two others.

This is just the case with
differences of intensity in sensations of light. Delboeuf's underlying
postulate.

Now, if the views which we have before enumerated with
regard to luminous intensities are accepted, it will be recognized that
the different hues of grey which Delboeuf displays to us are strictly
analogous, for our consciousness, to colours, and that if we declare
that a grey tint is equi-distant from two other grey tints, it is in the
same sense in which it might be said that orange, for example, is at an
equal distance from green and red. But there is this difference, that in
all our past experience the succession of grey tints has been produced
in connexion with a progressive increase or decrease in illumination.
Hence we do for the differences of brightness what we do not think of
doing for the differences of colour: we promote the changes of quality
into variations of magnitude. Indeed, there is no difficulty
here about the measuring, because the successive shades of grey
produced by a continuous decrease of illumination are discontinuous, as
being

(59) qualities, and because we can count approximately the
principal intermediate shades which separate any two kinds of grey. The
contrast A B will thus be declared equal to the contrast B C when our
imagination, aided by our memory, inserts between A and B the same
number of intermediate shades as between B and C. It is needless to say
that this will necessarily be a very rough estimate. We may anticipate
that it will vary considerably with different persons. Above 0 it is to
be expected that the person will show more hesitation and that the
estimates of different persons will differ more widely in proportion as
the difference in brightness between the rings A and B is increased, for
a more and more laborious effort will be required to estimate the number
of intermediate hues. This is exactly what happens, as we shall easily
perceive by glancing at the two tables drawn up by Delboeuf.[22]
In proportion as he increases the difference in brightness between the
exterior ring and the middle ring, the difference between the numbers on
which one and the same observer or different observers successively fix
increases almost continuously from 3 degrees to 94, from 5 to 73, from
10 to 25, from 7 to 40. But let us leave these divergences on one side:
let us assume that the observers are always consistent and always agree
with one another; will it then be established that the
contrasts A B and B C are equal ? It would first be necessary to

(60) prove that two successive elementary contrasts are
equal quantities, whilst, in fact, we only know that they are
successive. It would then be necessary to prove that inside a given tint
of grey we perceive the less intense shades which our imagination has
run through in order to estimate the objective intensity of the source
of light. In a word, Delboeuf's psychophysics assumes a theoretical
postulate of the greatest importance, which is disguised under the cloak
of an experimental result, and which we should formulate as follows:
" When the objective quantity of light is continuously increased,
the differences between the hues of grey successively obtained, each of
which represents the smallest perceptible increase of physical
stimulation, are quantities equal to one another. And besides, any one
of the sensations obtained can be equated with the sum of the
differences which separate from one another all previous sensations,
going from zero upwards." Now, this is just the postulate of
Fechner's psychophysics, which we are going to examine.

Fechner's psychophysics.
Weber's Law

Fechner took as his starting-point a law discovered by
Weber, according to which, given a certain stimulus which calls forth a
certain sensation, the amount by which the stimulus must be increased
for consciousness to become aware of any change bears a fixed relation
to the original stimulus. Thus, if we denote by E the stimulus which
corresponds to the sensation S, and by DE

(61) the amount by which the original stimulus must be
increased in order that a sensation of difference may be produced, we
shall have DE/E=const.

This formula has been much modified by the disciples of Fechner, and
we prefer to take no part in the discussion ; it is for experiment to
decide between the relation established by Weber and its substitutes.
Nor shall we raise any difficulty about granting the probable existence
of a law of this nature. It is here really a question not of measuring a
sensation but only of determining the exact moment at which an increase
of stimulus produces a change in it. Now, if a definite amount of
stimulus produces a definite shade of sensation, it is obvious that the
minimum amount of stimulus required to produce a change in this shade is
also definite ; and since it is not constant, it must be a function of
the original stimulus. But how are we to pass from a relation between
the stimulus and its minimum increase to an equation which connects the
" amount of sensation " with the corresponding stimulus ? The
whole of psychophysics is involved in this transition, which is
therefore worthy of our closest consideration.

The underlying assumption
and the process by which Fechner's Law is reached

We shall distinguish several different artifices in the
process of transition from Weber's experiments, or from any other series
of similar observations, to a psychophysical law like Fechner's. It is

(62) first of all agreed to consider our consciousness of
an increase of stimulus as an increase of the sensation S : this is
therefore called S. It is then asserted that all the sensations DS,
which correspond to the smallest perceptible increase of stimulus, are
equal to one another. They are therefore treated as quantities, and
while, on the one hand, these quantities are supposed to be always
equal, and, on the other, experiment has given a certain relation DE
= f (E)between the stimulus E and its minimum
increase, the constancy of DS is
expressed by writingDS= C(DE/f(E)
) C being a constant quantity. Finally it is agreed to replace the
very small differences DS and DEby the infinitely small differences dSand dE,
whence an equation which is, this time, a differential one: dS=C(dE/f(E))We shall now simply have to integrate on both sides to obtain the desired relation[23]:
S=C[integral](dE/f(E). made f É). And the transition will thus be made from a proved law, which only concerned the occurrence
of a sensation, to an unprovable law which gives its measure.

Without entering upon any thorough discussion

(63) of this ingenious operation, let us show in a few
words how Fechner has grasped the real difficulty of the problem, how he
has tried to overcome it, and where, as it seems to us, the flaw in his
reasoning lies.

Can two sensations be equal
without being identical?

Fechner realized that measurement could not be introduced
into psychology without first defining what is meant by the equality and
addition of two simple states, e.g. two sensations. But, unless they are
identical, we do not at first see how two sensations can be equal.
Undoubtedly in the physical world equality is not synonymous with
identity. But the reason is that every phenomenon, every object, is
there presented under two aspects, the one qualitative and the other
extensive ; nothing prevents us from putting the first one aside, and
then there remains nothing but terms which can be directly or indirectly
superposed on one another and consequently seen to be identical. Now,
this qualitative element, which we begin by eliminating from external
objects in order to measure them, is the very thing which psychophysics
retains and claims to measure. And it is no use trying to measure this
quality Q by some physical quantity Q' which lies beneath it : for it
would be necessary to have previously shown that Q is a function of Q',
and this would not be possible unless the quality Q had first been
measured with some fraction of itself. Thus nothing prevents us from
measuring the sensation of heat by

(64) the degree of temperature ; but this is only a
convention, and the whole point of psychophysics lies in rejecting this
convention and seeking how the sensation of heat varies when you change
the temperature. In a word, it seems, on the one hand, that two
different sensations cannot be said to be equal unless some identical
residuum remains after the elimination of their qualitative difference ;
but, on the other hand, this qualitative difference being all that we
perceive, it does not appear what could remain once it was eliminated.

Fechner's method of minimum
differences.

The novel feature in Fechner's treatment is that he did
not consider this difficulty mountable. Taking advantage of the fact
that sensation varies by sudden jumps while the stimulus increases
continuously, he did not hesitate to call these differences of sensation
by the same name : they are all, he says, minimum differences,
since each corresponds to the smallest perceptible increase in the
external stimulus. Therefore you can set aside the specific shade or
quality of these successive differences ; a common residuum will remain
in virtue of which they will be seen to be in a manner identical: they
all have the common character of being minima. Such will be the
definition of equality which we were seeking. Now, the definition of
addition will follow naturally. For if we treat as a quantity the
difference perceived by consciousness between two sensations which
succeed one another in the course of a continuous increase

(65) of stimulus, if we call the first sensation S, and
the second S + DS, we shall have to
consider every sensation S as a sum, obtained by the addition of the
minimum differences through which we pass before reaching it. The only
remaining step will then be to utilize this twofold definition in order
to establish, first of all, a relation between the differences DS
and DE, and then, through the
substitution of the differentials, between the two variables. True, the
mathematicians may here lodge a protest against the substitution of
differential for difference ; the psychologists may ask, too, whether
the quantity AS, instead of being constant, does not vary as the
sensation S itself ;[24]finally, taking
the psychophysical law for granted, we may all debate about its real
meaning. But, by the mere fact that DS
is regarded as a quantity and S as a sum, the fundamental postulate of
the whole process is accepted.

Break-down of the
assumption that the sensation is a sum, and the minimum differences
quantities

Now it is just this postulate which seems to us open to
question, even if it can be understood. Assume that I experience a
sensation S, and that, increasing the stimulus continuously, I perceive
this increase after a certain time. I am now notified of the increase of
the cause : but why should I call this notification an arithmetical
difference ? No doubt the notification consists in the fact that the
original state S has changed;

(66) it has become S'; but the transition from S to S'
could only be called an arithmetical difference if I were conscious, so
to speak, of an interval between S and S', and if my sensation were felt
to rise from S to S' by the addition of something. By giving this
transition a name, by calling it AS, you make it first a reality and
then a quantity. Now, not only are you unable to explain in what sense
this transition is a quantity, but reflection will show you that it is
not even a reality ; the only realities are the states S and S' through
which I pass. No doubt, if S and S' were numbers, I could assert the
reality of the difference S'-S even though S and S' alone were given ;
the reason is that the number S'-S, which is a certain sum of units,
will then represent just the successive moments of the addition by which
we pass from S to S'. But if S and S' are simple states, in what will
the interval which separates them consist ?
And what, then, can the transition from the first state to the second
be, if not a mere act of your thought, which, arbitrarily and for the
sake of the argument, assimilates a succession of two states to a
differentiation of two magnitudes ?

We can speak of
"arithmetical differences" only in a conventional sense

Either you keep to what consciousness presents to you or
you have recourse to a conventional mode of representation. In the first
case you will find a difference between S and S' like that between the
shades of the rainbow, and not at all an interval of magnitude. In the
second case you may intro-

(67) duce the symbol OS if you like, but it is only in a
conventional sense that you will speak here of an arithmetical
difference, and in a conventional sense, also, that you will assimilate
a sensation to a sum. The most acute of Fechner's critics, Jules
Tannery, has made the latter point perfectly clear. " It will be
said, for example, that a sensation of 5o degrees is expressed by the
number of differential sensations which would succeed one another from
the point where sensation is absent up to the sensation of 5o degrees .
. . . I do not see that this is anything but a definition, which is as
legitimate as it is arbitrary."[25]

Delbeouf's results seem
more plausible, but, in the end, all psychophysics revolves in a vicious
circle

We do not believe, in spite of all that has been said,
that the method of mean gradations has set psychophysics on a new path.
The novel feature in Delboeuf's investigation was that he chose a
particular case in which consciousness seemed to decide in Fechner's
favour, and in which common sense itself played the part of the
psychophysicist. He inquired whether certain sensations did not appear
to us immediately as equal although different, and whether it would not
be possible to draw up, by their help, a table of sensations which were
double, triple or quadruple those which preceded them. The mistake which
Fechner made, as we have just seen, was that he believed in an interval
between two successive

(68) sensations S and S', when there is simply a passing
from one to the other and not a difference in
the arithmetical sense of the word. But if the two terms between which
the passing takes place could be given simultaneously, there would then
be a contrast besides the transition ; and although the contrast is not
yet an arithmetical difference, it resembles it in a certain respect ;
for the two terms which are compared stand here side by side as in a
case of subtraction of two numbers. Suppose now that these sensations
belong to the same genus and that in our
past experience we have constantly been present at their march past, so
to speak, while the physical stimulus increased continuously : it is
extremely probable that we shall thrust the cause into the effect, and
that the idea of contrast will thus melt into that of arithmetical
difference. As we shall have noticed, moreover, that the sensation
changed abruptly while the stimulus rose continuously, we shall no doubt
estimate the distance between two given sensations by a rough guess at
the number of these sudden jumps, or at least of the intermediate
sensations which usually serve us as landmarks. To sum up, the contrast
will appear to us as a difference, the stimulus as a quantity, the
sudden jump as an element of equality: combining these three factors, we
shall reach the idea of equal quantitative differences. Now, these
conditions are nowhere so well realized as when surfaces of the same

(69) colour, more or less illuminated, are simultaneously
presented to us. Not only is there here a contrast between similar
sensations, but these sensations correspond to a cause whose influence
has always been felt by us to be closely connected with its distance;
and, as this distance can vary continuously, we cannot have escaped
noticing in our past experience a vast number of shades of sensation
which succeeded one another along with the continuous increase in the
cause. We are therefore able to say that the contrast between one shade
of grey and another, for example, seems to us almost equal to the
contrast between the latter and a third one; and if we define two equal
sensations by saying that they are sensations which a more or less
confused process of reasoning interprets as such, we shall in fact reach
a law like that proposed by Delboeuf. But it must not be forgotten that
consciousness has here passed through the same intermediate steps as the
psychophysicist, and that its judgment is worth here just what
psychophysics is worth ; it is a symbolical interpretation of quality as
quantity, a more or less rough estimate of the number of sensations
which can come in between two given sensations. The difference is thus
not as great as is believed between the method of least noticeable
differences and that of mean gradations, between the psychophysics of
Fechner and that of Delboeuf. The first led to a. conventional
measurement of sensation; the second

(70) appeals to common sense -in the particular cases
where common sense adopts a similar convention. In a word, all
psychophysics is condemned by its origin to revolve in a vicious circle,
for the theoretical postulate on which it rests condemns it to
experimental verification, and it cannot be experimentally verified
unless its postulate is first granted. The fact is that there is no
point of contact between the unextended and the extended, between
quality and quantity. We can interpret the one by the other, set up the
one as the equivalent of the other ; but sooner or later, at the
beginning or at the end, we shall have to recognize the conventional
character of this assimilation.

Psychophysics merely pushes
to its extreme consequences the fundamental but natural mistake of
regarding sensations as magnitudes

In truth, psychophysics merely formulates with precision
and pushes to its extreme consequences a conception familiar to common
sense. As speech dominates over thought, as external objects, which are
common to us all, are more important to us than the subjective states
through which each of us passes, we have everything to gain by
objectifying these states, by introducing into them, to the largest
possible extent, the representation of their external cause. And the
more our knowledge increases, the more we perceive the extensive behind
the intensive, quantity behind quality, the more also we
tend to thrust the former into the latter, and to treat our
sensations as magnitudes. Physics,

(71) whose particular function it is to calculate the
external cause of our internal states, takes the least possible interest
in these states themselves constantly and deliberately it confuses them
with their cause. It thus encourages and even exaggerates the mistake
which common sense makes on the point. The moment was inevitably bound
to come at which science, familiarized with this confusion between
quality and quantity, between sensation and stimulus, should seek to
measure the one as it measures the other : such was the object of
psychophysics. In this bold attempt Fechner was encouraged by his
adversaries themselves, by the philosophers who speak of intensive
magnitudes while declaring that psychic states cannot be submitted to
measurement. For if we grant that one sensation can be stronger than
another, and that this inequality is inherent in the sensations
themselves, independently of all association of ideas, of all more or
less conscious consideration of number and space, it is natural to ask
by how much the first sensation exceeds the second, and to set up a
quantitative relation between their intensities. Nor is it any use to
reply, as the opponents of psychophysics sometimes do, that all
measurement implies superposition, and that there is no occasion to seek
for a numerical relation between intensities, which are not superposable
objects. For it will then be necessary to explain why one
sensation is said to be more intense than another, and how the
conceptions

(72) of greater and smaller can be applied to things
which, it has just been acknowledged, do not admit among themselves of
the relations of container to contained. If, in order to cut short any
question of this kind, we distinguish two kinds of quantity, the one
intensive, which admits only of a " more or less," the other
extensive, which lends itself to measurement, we are not fax from siding
with Fechner and the psychophysicists. For, as soon as a thing is
acknowledged to be capable of increase and decrease, it seems natural to
ask by how much it decreases or by how much it increases. And, because a
measurement of this kind does not appear to be possible directly, it
does not follow that science cannot successfully accomplish it by some
indirect process, either by an integration of infinitely small elements,
as Fechner proposes, or by any other roundabout way. Either, then,
sensation is pure quality, or, if it is a magnitude, we ought to try to
measure it.

Thus intensity judged (1)
in representative states by an estimate of the magnitude of the cause
(2) in affective states by multiplicity of psychic phenomena involved

To sum up what precedes, we have found the notion of
intensity to present itself under a double aspect, according as we study
the states of consciousness which represent an external cause, or those
which are self sufficient. In the former case the perception of
intensity consists in a certain y estimate of the
magnitude of the cause by means of a certain quality in the
effect : it is, as the Scottish philoso-

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